Directive antenna system



Oct. 30, 1928.

Filed June 27. 1925 7 4 5 Mk9 2 m w M a: 6

f 7 6 B M 7 9 0:6 6

w 7 M M 4 a S .E 7 66 W/ ATTORNEY Patented Oct. 30, 1928.

ATEVNT OFFICE.

FRANK CONRAD, or PITTSBURGH,- PENNSYLYANIAJ," Assiomm' To WnsrmenofisnELECTRIC & MANUFACTURING COMPANY, A COEBPOZRATION or PENNSYLVANIA".

.,.DI'BECTIVE AnTnNNAsYsTEM.

Application fi1ed J'i1ne27, 1925. Serial K633193119.

' invention relatesfto radio ignallin systems, and particularly tolantennain'e'ans operable therewith and'ca pableof producnig directiveeffects upon the signalling Waves.

An object or" my invention islto provide an antenna systenr havingmarked directive properties. I v

Anotherobject of my invention is'to pro vide an antenna systemresponsive toradlo Waves in one direction. f

Another object of my invention is to produce a multiple antenna systemhaving a single tuning means.

Another object of my inventionis'to provide a multipleantenna, andtuningmeans cooperating with a transfer means for a radio detector. y 7Another object of my invention is'to provide a receiving antenna whichis'less-rosponsive to staticdistu'rbances.

Another object ofmy invention is to provide a radio antenna whichis-adapted for a radio relaying system. U f

In prior reception of radio signals, many systems have been proposed forobtaining directional selectivity. These systems, have, however beensubjectto various faults and inconveniences. A plurality of antennaehasbeen set in a row, normal to the desired direction of the signal Wave.Very many difficulties have,,hoWever, been experiencedwlth such asystem. As it is required that all oi the antenna systems be tuned tothe same oscillation frequency, elaborate prov slons have been necessaryfor accomplishing that result. The desired results have notbeen-obtained because of the difii'culty' of tuning a large number ofseparate inductors to the same oscillation frequency;

My invention embodies a plurahty of antenna devices positionediin a IOWand ot substantially equal electrical characterlstics. The systemfurther embodied bridle ires connected to the antenna devices and to asingle tuning coil in suchWay that the effective length of the bridleWires to'the'coil s substantially the same for each antenna system, thussecuring a tuning means for} all of the antenna systems whichcontrolsjthe trefquency of all simultaneously and holds them atthe samevalue.- The interconnection provides aclose coupling between thevarious'circuits Which causes them to oscillate at the sametrequencyyeven though the structures are slightly different and haveslightly different separate resonant frequencies. My in ventlon turtheifprovides a transfer'lineh-om the antenna system to a radio detector fromnvl1ich an audio frequency output maybe con'-' veye'd to a broadcastinstation.

Other objects'and structural details o1" my nvention Will be apparentfrom the followi g'description when rcadin connection with theaccompanying drawings; wherein systems 1, 2, 3 and l which' areprefera'bly' similar in sizeandconstruction. The antenna systemsmaylconsist of poles 5 to each of Which is attacl'iedcounterpoiseconductor 6 consisting of copper rod'and an aerial 7consisting of another copper rod of substantially equalsize. Both theaerials and the counterpoises are supported by insulators 8Q yAdditional poles 9 are placed'nearto api'ces of isosceles trianglesformed upon a base line oi pairs of the poles 5. i Upon the poles 9 aremounted insulators 11 and 12. Bridle Wires 14 are attached tothelower'endsot' the antenna structures 7 and supported upon theinsulators 12. Other bridle Wires 15 areat tached to the upper'ends ofthe counterpoise structures (3 and supported upon the insulators 11. 1"

7 Another pole l6 is provided which is positioned near the apex of anisoscelestriangle formed upon the base line between the poles 9.Insulators 17 and'18'areattach'ed to the pole 16 and bridle Wires19 and20 are supported thereon, near the midpoint, and the ends attached, asshown, to the bridle Wires 14'a 'd'15at the points of supportuponinsulators 1 1' and'12. A tuning inductance'21 is supported 'uponthepole 16. Its terminals are connected .tothe bridle Wires 19 and 2O attheir midpoints' upon the insulators 17 tion of the inductance in .thedetector 28.

The audio-frequency output of the detector 28 may be conveyed by anordinary metallic transmission line 29 to a radio broadcasting station,or to such other apparatus as it is desired to energize by theaudio-frequency currents.

In the operation of my device as a radio receiving antenna, radiowavesfrom a direction normal to the plane of the antenna systems will strikethe various elements in zerophase displacement and all will be set intooscillation simultaneously and in phase. The oscillatory currents willflow between the aerials 7 and counterpoises 6 through the bridle wires14 and-15, 19 and 20 and the inductor '21. Because of the constructionshown, the length of circuit of each antenna through the inductor 21 issubstantially equal to that of all of the others and, therefore, sincethe antenna and counterpoise elements are also similar, the naturalresonant frequencies'are the same. The current flowing in the coil 21 isthen the result of energy icked up by the four antenna systems, and ISin phase, and thus re-inforced.

The complete antenna system shows marked directive properties, asindicated by the curve of Fig. 2. ,Inthis curve, the horizontal axis isindicated as the line through the various antenna structures. Thepronounced directive quality then becomes evident from the shape of thecurve.

The theoretical reason to be assigned for this. directive effect may beunderstood from an inspection of Fig. 3 in which the antenna andcounterpoise systems are indicated by the circles 31, 32, 33 and 34.,Sine waves 35, forming a wave front, are indicated as impinging upon thefour antennae from a remote station, at an angle normal to the line ofthe antennae system. It will be ob vious that the wave front strikes thefour antennae simultaneously and induces in them currents which are inphase, which currents,

therefore, reinforce each other through the coil 21. Another sine-wavecurve 36 is represented as traversing a line parallel to the line of theantennae and it will be evident 1 that the wave front strikes theantennae successively and that,therefore, when antenna flow in theopposite direction. This is particularly the case if the separation ofthe end antennae is the same as a wave length of the signal to whichthey are resonant, or an'odd multiplethereof. r. I

- This property has been foundparticularly convenient for the relayingof signals from an eastern pointto a western point in the, 7

United States, since ithas been found that the 'major portion of thetroublesome static which tends. tointerfere with the relay'sigf nals,originates in or near the Gulf of Mexico at a point almost due south ofthe receiving antenna systems. The received signals then come from adirection almost at 90 fromthe interfering static, this situationpermits optimum utilization of the direction-selective properties of theantenna system.

By means of the system of my invention, I am enabled to provide a radioantenna system having marked'direction selectivity and markedsuperiority for the reception ofsignal energy over the antenna of theprior art.

While I have shown but a single: embodiment of my invention, lt lScapable of various modifications and it is desired, therefore, that onlysuch limitations shall be imposed thereon as are required by the priorart or indicated in the appended claims.

I .claim as my invention:

1. A radio. antenna system comprising a plurality of insulating'supportingfmeans linearly positioned, pairsof aerialand coun- Isignals, a plurality of'pairs of aerial and counterpoise members, onepair being supported. on each of said supporting means, bridle wiresconnected to said members, in-

sulating supports therefor, and a single inductor connected thereto, aconveying circuit connected thereto, and a radio-signal responsive meanscooperating therewith. I

. 3. A radio receiving arrangement, comprising a plurality of systems,each system comprising an aerial and an associated counterpoise, aplurality of pairs of bridle wires, the members of any one pair beingconnectedto an aerial and its associated counterpoise, the bridle wiresconnected to aerials being connected together and thereby connectingconjugate points of the aerials, the bridle wires connected tocounterpoises being connected together and thereby connecting conjugatepoints of the counterpoises and atuning coil connected to the bridlewires.

In testimony whereof, I have hereunto subscribed my name this 4th day ofJune, 1925.

FRANK CONRAD;

